Hypercholesterolemia is known to be one of the prime risk factors for ischemic cardiovascular disease, such as arteriosclerosis. Bile acid sequestrants have been used to treat this condition; they seem to be moderately effective but they must be consumed in large quantities, i.e. several grams at a time and they are not very palatable.
MEVACOR.RTM. (lovastatin) and ZOCOR.RTM. (simvastatin), now commercially available, are members of a group of very active antihypercholesterolemic agents that function by limiting cholesterol biosynthesis by inhibiting the enzyme, HMG-CoA reductase.
Squalene synthase is the enzyme involved in the first committed step of the de novo cholesterol biosynthetic pathway. This enzyme catalyzes the reductive dimerization of two molecules of farnesyl pyrophosphate to form squalene. The inhibition of this committed step to cholesterol should leave unhindered biosynthetic pathways to ubiquinone, dolichol and isopentenyl t-RNA.
Previous efforts at inhibiting squalene synthase have employed pyrophosphate or pyrophosphate analogs containing compounds such as those described in P. Ortiz de Montellano, et al., J. Med Chem., 20, 243 (1977) and E. J. Corey and R. Volante, J. Am. Chem. Soc., 98, 1291 (1976). S. Biller (U.S. Pat. No. 4,871,721) describes isoprenoid (phosphinylmethyl)phosphonates as inhibitors of squalene synthase.
Recently certain nonphosphorous containing inhibitors of squalene synthase have been isolated as natural products. These natural product inhibitors are described in U.S. Pat. Nos. 5,102,907; 5,132,320; 5,096,923; 5,026,554; 5,055,487; and 5,053,425. A need still remains for a more effective squalene synthase inhibitor, i.e. one that provides a greater antihypercholesterolemic effect and exhibits a good safety profile.
The present invention is directed to semi-synthetic analogs of the above-noted natural products, and a novel process for making them.